Flat cable wiring systems have come into existence in recent years and are usable under certain conditions specified in the National Electrical Code (NEC). Such cable is defined in the code as type FCC. The NEC does not specify a maximum number of conductors that can exist in type FCC cable but does specify that there shall be three or more. Furthermore, the NEC requires that in any type FCC 2-wire system with grounding the grounding conductor must be central. This has been interpreted by certifying agencies to require that the grounding conductor of a type FCC 3 or 4 wire cable be located intermediate the outermost conductors.
Prior flat cable systems have not adequately provided transition assemblies which are capable of interconnecting type FCC cables with other forms of wiring systems and also with other FCC cables in a way which is fully satisfactory. In particular, those systems which are capable of, for example, connecting a 4-conductor FCC cable to one or more 3-conductor branch circuit FCC cables use 4-conductor cable for all of the cables. The selection of conductors to be interconnected at a transition point then depends upon the manner in which the interconnection device is assembled or used. The result is that in a branch circuit cable of a 2-wire grounded system, one of the conductors in a 4-conductor cable is simply not used.